1899] Odell — Freshwater Polvzoa. 109 



(i) Plumatella repens, L. 



The colonies of Plumatella are formed of sheaths 

 or coverings called coenoecia which the polypides secrete, 

 and appear as brownish tubes branching like tiny 

 trees or seaweeds, extending over a surface measuring some- 

 times several square feet. There are two modes of attachment 

 in these colonies: (a) where the lower portion of the stem is 

 fixed and the remainder of the branch floats freely : (//) when 

 the whole branch is closely adherent or creeping on the sub- 

 merged object. 



At the extremity of each branch a polypide protrudes, 

 exposing the lophophore or plume-like organ (hence the name 

 Plumatella). The polypides quickly retreat on the slightest 

 alarm or disturbance, and remain in their sheaths until quite 

 satisfied that the cause is removed. 



" The body of the polypide* is a transparent membraneous 

 sac with a lophophore (horse-shoe shaped in this genus), on 

 which are arranged the tentacles. Each tentacle is capable of 

 independent motion, is ciliated on both sides, and is the only 

 means the polypide has of receiving impressions. The mouth 

 is at the fore end, the rest of the body being concealed in a 

 brown sheath or ccenoecium. The mouth has on one border a 

 tongue-like organ called the Epistome, which can close the open- 

 ing, and prevent the escape of food. Extending from the mouth 

 to the stomach is the oesophagus. The stomach is a widened 

 tube, conspicuous by its contents. 'It is suspended in the hollow 

 body, and is bathed by a colorless fluid which fills the body 

 cavity and extends to the hollow tentacles. The stomach is 

 followed by a tubular intestine which curves forward, opening 

 on the lophophore." The polypide has no heart nor circulatory 

 system. The body has a beautifully developed muscular system, 

 which enables it to move freely and rapidly. One set of mus- 

 cles everts the body, another set is used in expanding the various 

 tentacles of the lophophore ; and another set supports the body 



Dr. A. C. Stockes in " Aquatic Microscopy "' p. 242. 



